The 90-foot-long foam Argentinosaurus was one of 34 dinosaurs in an interactive exhibit, "Field Station: Dinosaurs."
"A welder was working nearby and a spark set it off," Police Capt. Scott Tamagny told Daily Voice.
"No other dinosaurs were affected," Tamagny said, adding that no injuries were reported.
The exhibit, scheduled to open on Memorial Day weekend, found a home in Bergen County after being evicted from Secaucus.
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